Websites scenario tests

This PR fixes a few issues:

(1) Fixes test setup and cleanup issues for websites tests
(2) Fixes several test issues in the websites tests
(3) fixes path issues in the websites cmdlets for websites scaffolding pieces (TFS: 1703783)
(4) Adds a powershell script for runnign the websites tests separately
(5) Adds infrastructure for declaring required environment variables with a test
Why we need this?